Study on the characteristics of pressure relief spread and pressure reconstruction in pumped concrete

Abstract

The pressure relief and backflow of concrete during the swing of the distribution valve are major causes of pumping pulses in dual-plunger concrete pumping systems, which significantly disrupt the continuity of concrete delivery. In this study, we independently developed an experimental platform for concrete pulse pumping and a platform for pressure relief spread experiments. Using concretes with different rheological properties, pulse pumping and pressure relief spread experiments were conducted. The results indicate that: (1) Pumping pulses lead to the alternation of "pressure relief spread (PRS)" and "pressure reconstruction (PCR)" within the pipeline. (2) PRS mainly occurs in the middle and later sections of the pipeline, where large pipe diameters and high water-cement ratios enhance concrete flowability and spread capability, while higher pressure inhibits spread by increasing cohesion and compressibility. (3) At the start of each pumping cycle, pipeline pressure must be re-established to overcome the maximum static friction between the concrete and the inner wall, after which steady pumping is achieved with a slight pressure drop. As the water-cement ratio increases, the maximum pressure values at different points in the pipeline become less pronounced. (4) The PCR near the pipeline outlet is slightly slower, but this time difference is minimal, and nearly all points reach the maximum pressure simultaneously. Through experimental research, this study clearly demonstrates the behavior and characteristics of concrete within pipelines during pulse pumping in traditional dual-plunger systems. This study demonstrates that optimizing the water-cement ratio and pipeline diameter configuration reduces the pressure required to overcome static friction, thereby lowering peak pumping pressure. This mitigation diminishes pipeline impact, equipment vibration, and structural fatigue. The findings provide a critical theoretical foundation for eliminating pulsating pumping effects, achieving continuous concrete delivery, prolonging equipment longevity, and facilitating intelligent upgrades in concrete pumping systems.